1. Field of the Invention
The present invention relates to a light exposure control device, and a light exposure apparatus containing the light exposure control device. More particularly, the invention pertains to a light exposure control device and a light exposure apparatus for curing light sensitive adhesives. In the light exposure apparatus, light is preferably emitted by an optical fiber arrangement.
2. Description of the Related Art
A wide variety of means are known to control the illumination of a light exposure apparatus. For example, the illumination from the light source can be controlled by changing the current or voltage of the light source or by changing the effective phase section of the current. U.S. Pat. No. 6,515,430 shows a typical light exposure device including a lamp for shining light through a light delivery device which can be an optical fiber. Between the lamp and the optical fiber are a shutter and a diaphragm which controls the duration and intensity of light sent from the lamp to the optical fiber.
In other illumination control techniques, a neutral or gray wedge, a filter or a similar absorptive device can be placed in the optical path between the light source and the optical fiber. However, varying the illumination density by means of a gray wedge is limited and does not permit unobstructed directing of light, but will always reduce maximum illumination. It is also known in the art that the brightness of the light emitted by fiber optical lamps may be controlled by means of a built-in iris diaphragm. U.S. Pat. Nos. 2,735,929 and 3,222,510 show a standard iris diaphragm. U.S. Pat. Nos. 2,336,119; 3,371,202; 4,018,527; 4,257,086; and 6,102,554 show an iris type diaphragm structure which operates in a fashion similar to a standard camera lens. However, an iris diaphragm will change the entrance angle of the light into the optical fiber and the exit angle of the light emanating from the optical fiber. Sectored diaphragms have the disadvantage that at least one diaphragm sector will remain in the light path even at maximum aperture and thus will reduce the maximum illumination that would otherwise be possible with the specific light source and light transmission capacity of the system. U.S. Pat. No. 4,425,599 proposes the use of a rotatable diaphragm disc having a single, sickle-shaped aperture of varying width between the light source and the optical fiber. By suitable selection of the shape of the sickle-shaped opening in the diaphragm disc, and the angular position of the rotatable diaphragm, a desired illumination is provided to the optical fiber. U.S. Pat. No. 6,850,367 also shows a diaphragm plate having a single arcuate opening, or a series of discrete sectored openings of various sizes around the plate. U.S. Pat. No. 4,834,071 shows a rotary shutter plate having a spiral periphery for use as a diaphragm an illumination controller. In this patent, a rotary shutter plate has an opening angle corresponding to the irradiation time or the luminance of a light beam to be fed to a light guide. U.S. Pat. No. 7,008,070 shows an illumination device and projector wherein a filter has alternating light transmission and non-transmissive rectangular areas. By rotating a holder, filtering films optically convert a light beam. U.S. Pat. No. 5,748,816 shows an optical cavity for receiving light parallel to an optical axis. An interior of a tube has sheet metal plates perpendicular to the optical axis of the tube, which are formed as aperture diaphragms with openings that become smaller along the optical axis of the tube in the direction of the incident radiation. U.S. Pat. No. 5,016,975 shows a light-emitting unit having a variety of discrete diaphragm shapes.
It has been determined that a problem with these aperture arrangements is non-uniformity of light intensity. The present invention provides a light exposure apparatus having improved uniformity of light intensity by means of a diaphragm having multiple openings positioned on the planar face of the diaphragm which have a continuously tapered width. These multiple tapered openings account for the top, middle, and bottom of the lamp light intensity range, whereas a single opening diaphragm of the prior art accounts for only one portion of the lamp light intensity range, usually, the middle portion.